Here is the hardware you are looking for. You should find this at Lowes or Home Depot, but you'll have to search. It'll be in the lamp parts area with harps and other things.

It has this notch near the edge. What you are doing is making a hole about 1 inch in diameter, and squeeze these prongs and stick the sucker in the fish and set it so the cut out in the prong gets fish in it to hang onto. Below I have used a piece of cardboard to demonstrate.

A puffer fish is VERY tough. I started by drilling a set of holes in the fish to act as a guide. I drilled more and more holes until I was close to making a full circle cutout. I then used some heavy snips to cut around. I found I needed the hole to be bigger and it was tough going. These guys stink too. You have to be careful not to damage the quills as you do this, so try to be gentle.

Use a lot wattage bulb.

That's all there is to it. The tough part is cutting the hole without damaging the fish. A jig saw would work if you had one.

Here is mine from the top. He's a big mutha, which made it a bit easier, but, maybe he's a bit thicker.
_________________Announcing Swank Pad and Crazy Al's Molokai Maiden!

I found a lady who sales blowfish. She didn't have any of the large ones in but is getting more, she sales them for $29. Seems like a fare price to me. I did buy a medium one for $7.50.
_________________Original Art by
Scott "Flounder" Scheidly
www.flounderart.com

When we were coming back from Hukilau we stopped at gas staion souvenir shop that had lots of dead critters, including small puffers. I plan to pick up about a dozen next time for a new project I have in mind. Gotta get them cheap as possible.
_________________Announcing Swank Pad and Crazy Al's Molokai Maiden!

tiki-riviera -- check out Display & Costume Supply, they're on Roosevelt near Northgate Mall. They have a large year-round Christmas display section, including a large area dedicated just to single colored bulbs in an array of different sizes. While you're there, check out their tropical display section -- they're the area's source for thatch & such.

Yeah, the fixture takes regular Christmas bulbs, and when you are a lamp freak like me, you have a box full of all size and shape bulbs around at all times...
_________________Announcing Swank Pad and Crazy Al's Molokai Maiden!

Swanky, I'm a fellow lamp freak as well. I have been trying to get rid of them lately but it's hard to give em up.
Can't wait to make my tiki room and add these.
_________________Original Art by
Scott "Flounder" Scheidly
www.flounderart.com

Swanky,
Your post inspired me to complete my own puffer-fish lamp. (It had been hanging, unilluminated, for a couple years.) I cracked the guy a little bit drilling the hole but a touch of gorilla glue fixed that.
Now it's just a matter of choosing a color for the bulb.